Various ambulatory medical devices are known for pumping drugs and other fluids to a patient from a fluid reservoir. Ambulatory drug pumps may include a rotatable cam shaft which has one or more cams that activate one or more tube engaging members in a particular sequence to pump fluid through the tube, as in a peristaltic pump.
An example of a peristaltic type pump is described and shown in U.S. Pat. No. 4,559,038, issued Dec. 17, 1985, to Berg et al., incorporated herein by reference. In U.S. Pat. No. 4,559,038, a rotating cam shaft is provided with three cams. Each cam engages one of two reciprocating valve followers or a reciprocating expulsor follower. The valve followers and expulsor follower engage a tube which provides fluid communication between a fluid reservoir and the patient. The rotating cam shaft moves the valve followers and expulsor follower in appropriate manners to pump fluid through the tube.
Ambulatory drug pumps frequently have a power supply including a replaceable battery or other replaceable or rechargeable power supply. Energy consumption is a significant concern. The shorter the life of the power supply, the more frequently the power supply must be replaced or recharged.
Peak torque loads applied to the cam shaft can also be a significant concern. If the peak torque loads that occur during operation exceed the demand capability of the power supply, the pump may stop operating. The patient drug therapy may be interrupted. This could be potentially harmful to the patient. Also, relatively large power supplies may be needed to ensure that the maximum torque loads do not stop the pump.
There is a need for peristaltic pump apparatus for pumping fluid to a patient where total energy consumption is emphasized to improve or maximize performance. There is also a need for peristaltic pump apparatus for pumping fluid to a patient where peak torque loads are emphasized to maximize or improve performance. Further, there is a need for methods of design and manufacture of rotatable cams and reciprocally mounted followers that emphasize total energy consumption and peak torque loads to improve performance for existing designs and to maximize performance for new designs.